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WASHINGTON, D.C. July 28, 2009 -- A group of researchers at Johns Hopkins University has designed nanoparticles that can carry cancer-treating radioisotopes through the body and deliver them selectively to tumors. Today in Anaheim, CA, they will report the latest results of their research, including studies in animal models, at the 51st meeting of the American Association of Physicists in Medicine (AAPM).

The nanoparticles are made with a commercially available product known as "liposomes" -- small chemical spheres made of fatty molecules that can package drugs and other chemicals. Liposomes are a powerful emerging tool in medicine because they can be designed to carry many different drugs and manipulated to control how long they stay in the bloodstream. One type of liposome, Doxil, is already approved by the U.S. Food and Drug Administration (FDA) for delivering Doxorubicin, a chemotherapeutic that is toxic to the heart.

The Hopkins scientists are using liposomes that have been modified with antibodies, a class of immune system proteins that recognize and bind to many different microscopic targets -- bacteria, viruses, other proteins, and human cells. Some antibodies specifically bind to cancer cells, and by attaching these cancer-specific antibodies to the liposomes, the scientists have created "immunoliposomes," which will wend their way through the bloodstream and seek out tumors inside the body. When they come into contact with their target cells, they deliver their payload into the cells.

"It's a promising approach to solving the problem of how to deliver more of a therapeutic to cancer cells," says George Sgouros, a radiology professor at Johns Hopkins who led the research.

Similar studies by other groups of researchers have already demonstrated how immunoliposomes could be packaged with tiny radioactive tracers used for imaging tumors. What Sgouros and his colleagues have done is figure out how to reproducibly package much more powerful radioisotopes, called alpha-particle emitters that have the ability to kill cancer cells without damaging nearby normal cells, and they have tested how effectively they can treat mice with a very aggressive type of metastatic breast cancer.

Early results show that they can pack a relatively large dose of radionuclides into the liposomes and substantially extend the life of treated mice.

"This treatment is much less toxic than chemotherapy because it is targeted to tumor cells rather than to all rapidly dividing cells " says Sgouros. "Nanoparticles designed to deliver these powerful isotopes have a great potential in cancer therapy, particularly for metastatic disease."

MORE INFORMATION

The talk "Immunoliposomes for Targeted Radionuclide Therapy" is at 2:45 p.m. on Tuesday, July 28 in Room 303A. See here »

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PRESS REGISTRATION

Journalists are welcome to attend the conference free of charge. AAPM will grant complimentary registration to any full-time or freelance journalist working on assignment. The Press guidelines are posted at: http://www.aapm.org/meetings/09AM/VirtualPressRoom/.

If you are a reporter and would like to attend, or if you have questions about the meeting, contact Jason Bardi (jbardi@aip.org, 858-775-4080).

ABOUT MEDICAL PHYSICISTS

If you ever had a mammogram, ultrasound, X-ray, MRI, PET scan, or known someone treated for cancer, chances are reasonable that a medical physicist was working behind the scenes to make sure the imaging procedure was as effective as possible. Medical physicists help to develop new imaging techniques, improve existing ones, and assure the safety of radiation used in medical procedures in radiology, radiation oncology and nuclear medicine. They collaborate with radiation oncologists to design cancer treatment plans. They provide routine quality assurance and quality control on radiation equipment and procedures to ensure that cancer patients receive the prescribed dose of radiation to the correct location. They also contribute to the development of physics intensive therapeutic techniques, such as the stereotactic radiosurgery and prostate seed implants for cancer to name a few. The annual AAPM meeting is a great resource, providing guidance to physicists to implement the latest and greatest technology in a community hospital close to you.

ABOUT AAPM

The American Association of Physicists in Medicine (AAPM) is a scientific, educational, and professional organization of more than 6,000 medical physicists. Headquarters are located at the American Center for Physics in College Park, MD. Publications include a scientific journal ("Medical Physics"), technical reports, and symposium proceedings.
See: www.aapm.org.